1. Field of the Invention
The present invention relates to an organic electroluminescence panel where organic EL elements, each having at least an organic light emitting layer between a pair of electrodes, are arranged in matrix.
2. Description of the Related Art
Organic electroluminescence (hereinafter referred to as EL) panels have been receiving attention as one of the next generation flat displays to take place the liquid crystal displays. In the display panels (hereinafter referred to as an organic EL panel), the color of light emitted by each pixel can be determined depending on the kind of light emitting material used to form an organic light emitting layer for the pixel. Thus, pixels for different color light are formed so that RGB display can be realized.
In this organic EL panel, bright display is achieved by increasing the amount of current supplied to each organic EL element. However, increase of a current amount results in reduction of the service life of an organic EL element. Therefore, instead of increasing a current amount, it is desired to ensure the largest possible area for a light emitting region, or an aperture ratio, in each pixel.
A larger aperture ratio enables brighter display while suppressing current supplied to the organic EL element to a relatively small amount (See Japanese Patent Laid-open Publication No. 2001-290441). Increase of an aperture ratio means increase of the proportion of the light emitting region of an organic EL element relative to the entire area of each pixel.
Here, in an organic EL panel of an active type, at least two TFTs are provided in each pixel to drive the concerned organic EL element. Specifically, a driver TFT for controlling a driving current supplied to the organic EL element is arranged between the power supply line and the organic EL element in the circuit structure. That is, the driver TFT is positioned close to the power supply line and the organic EL element in a two-dimensional arrangement. Moreover, the driver TFT, which controls a driving current to be supplied to the organic EL element according to a gate voltage, has a long gate length. With these factors, appropriate positioning of the driver TFT is difficult to achieve.
Further, the gate line of a driver TFT must be placed detouring around the contacts of the source and drain electrodes located at both ends of the driver TFT. Wiring in this manner results in a problem of reduction of an aperture ratio.